For the study, published Aug. 15 in the journal Diabetologia, researchers followed more than 22,000 people in Greece for about 11 years. During that time, about 2,300 of them developed diabetes.

The researchers examined the participants' eating habits and developed a 10-point Mediterranean diet score. Participants with scores above six were 12 percent less likely to develop diabetes than those with Mediterranean diet scores of three or lower, they found.

People with the highest levels of carbohydrates in their diets were 21 percent more likely to develop diabetes than those with the lowest carbohydrate intake. People with a high Mediterranean diet score and low carbohydrate intake were 20 percent less likely to develop diabetes than those with a low Mediterranean diet score and high carbohydrate intake, according to the study.

"The role of the Mediterranean diet in weight control is still controversial, and in most studies from Mediterranean countries the adherence to the Mediterranean diet was unrelated to overweight," said Dr. Carlo La Vecchia and colleagues from the Mario Negri Institute of Pharmacological Research in Milan, Italy.

"This suggests that the protection of the Mediterranean diet against diabetes is not through weight control, but through several dietary characteristics of the Mediterranean diet," they said in a journal news release. "However, this issue is difficult to address in cohort studies because of the lack of information on weight changes during follow-up that are rarely recorded."

Although the study showed an apparent association between a Mediterranean diet and a lowered risk for type 2 diabetes, it did not prove cause-and-effect.